Workpiece processing apparatus and workpiece processing method

Abstract

A workpiece processing apparatus including a control unit that is provided with a storage medium on which a polishing load measured when an upper turn table is moved downward to a fixed position in a state wherein the workpiece is properly held in holding hole of the carrier is recorded in advance, calculates a difference between a polishing load measured when upper turn table is moved downward to the fixed position in a state wherein the workpiece is held in holding hole of the carrier and the polishing load recorded on the storage medium, and judges the occurrence of abnormal holding of the workpiece if the calculated difference exceeds a threshold value. As a result, it becomes possible to detect abnormal holding of a workpiece in a short time with a high degree of precision before the workpiece is processed and prevent breakages of the workpiece and the processing apparatus.

The invention claimed is: 
     
       1. A workpiece processing apparatus, comprising:
 an upper turn table, 
 a load cell disposed above and connected to the upper turn table, 
 a lower turn table, 
 a carrier having a holding hole for a workpiece, the carrier configured to be interposed between the upper turn table and the lower turn table, the workpiece having an upper surface and a lower surface, and 
 a control unit that is provided with a storage medium on which a reference polishing load measured when the upper turn table is moved downward to a fixed position in a state in which the workpiece is properly held between the upper turn table and the lower turn table in the holding hole of the carrier is recorded in advance, the control unit being configured to:
 calculate a difference between a polishing load measured via the load cell that connects to the upper turn table when the upper turn table is moved downward to the fixed position in a state in which the workpiece is held between the upper turn table and the lower turn table in the holding hole of the carrier and the reference polishing load recorded in advance on the storage medium, and 
 before the workpiece is processed, judge an occurrence of abnormal holding of the workpiece if the calculated difference exceeds a threshold value; 
 
 wherein the workpiece processing apparatus is configured such that both surfaces of the workpiece can be processed at a same time when the workpiece is held in the holding hole of the carrier and the carrier is interposed between the upper turn table and the lower turn table. 
 
     
     
       2. The workpiece processing apparatus according to  claim 1 , wherein
 the workpiece processing apparatus is a double-side polishing apparatus or a double-side lapping apparatus. 
 
     
     
       3. The workpiece processing apparatus according to  claim 2 , wherein
 the control unit is configured to update the reference polishing load recorded on the storage medium in advance in accordance with temporal changes in a polishing pad of the double-side polishing apparatus or a lapping turn table of the double-side lapping apparatus. 
 
     
     
       4. A workpiece processing method comprising steps of:
 providing a workpiece processing apparatus comprising an upper turn table, a load cell disposed above and connected to the upper turn table, a lower turn table, a carrier having a holding hole for a workpiece, the workpiece having an upper surface and a lower surface, the carrier configured to be interposed between the upper turn table and the lower turn table, and a control unit, the workpiece processing apparatus being capable of processing both surfaces of the workpiece at a same time by holding the workpiece in the holding hole of the carrier by inserting the workpiece thereinto, moving the upper turn table downward to a fixed positioner thereby interposing the carrier holding the workpiece between the upper turn table and the lower turn table; 
 recording in advance a reference polishing load measured when the upper turn table is moved downward to the fixed position in a state in which the workpiece is properly held between the upper turn table and the lower turn table in the holding hole of the carrier, the recorded reference polishing load being recorded in a storage medium of the control unit; 
 measuring a polishing load via the load cell that connects to the upper turn table, the polishing load being measured after the upper turn table is moved downward to the fixed position in a state in which the workpiece is held between the upper turn table and the lower turn table in the holding hole of the carrier; 
 calculating a difference via the control unit between the polishing load measured via the load cell when the upper turn table is moved downward to the fixed position in a state in which the workpiece is held between the upper turn table and the lower turn table in the holding hole of the carrier and the recorded reference polishing load; and 
 if the calculated difference exceeds a threshold value before the workpiece is processed, judging an occurrence of abnormal holding of the workpiece via the control unit, moving the upper turn table upward from the fixed position, ejecting the workpiece from the holding hole of the carrier, reinserting the workpiece into the holding hole of the carrier and, after reinsertion, processing the workpiece if a calculated difference assessed after reinsertion does not exceed the threshold value; wherein processing the workpiece comprises polishing both surfaces of the workpiece at the same time. 
 
     
     
       5. The workpiece processing method according to  claim 4 , wherein
 the processing performed on the workpiece is double-side polishing or double-side lapping. 
 
     
     
       6. The workpiece processing method according to  claim 5 , comprising a step of:
 updating the reference polishing load recorded in advance in accordance with temporal changes in a polishing pad which is used in the double-side polishing or a lapping turn table which is used in the double-side lapping.